Method and apparatus for diffusing ozone gas into liquid

ABSTRACT

An ozone diffuser includes an outer tube having a tubular porous membrane disposed coaxially therein. An annular space is defined between the inner surface of the tubular member and the outer surface of the membrane into which ozone gas is applied. Water is caused to flow through the interior of the membrane in such a manner as to form a vortex which creates a negative pressure at the inner surface of the membrane. The pressure difference between the annular space and the interior of the membrane causes ozone gas to be sucked through the membrane and become diffused into the water. The pressure difference results in a high concentration of ozone in the water. The vortex also produces a shearing effect which breaks up the ozone bubbles and increases the diffusion efficiency.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention generally relates to the art of cleaningand sterilization, and more specifically to a method and apparatus fordiffusing ozone gas into a liquid which is used for these purposes.

[0003] 2. Description of the Related Art

[0004] The use of ozone for cleaning or sanitizing objects is known inthe art per se. Ozone is vastly superior to chlorine and other commonlyused sanitizing agents which are toxic and must be removed after use.Ozone is also a much stronger sanitizing agent than such other fluids.

[0005] U.S. Pat. No. 4,898,679, entitled “METHOD AND APPARATUS FOROBTAINING OZONE SATURATED WATER”, issued Feb. 6, 1990 to Seymour Siegelet al, teaches how to use ozone saturated water to performclean-in-place cleaning of pipes in a processing plant. Other usesinclude sanitization of fruit and other agricultural products.

[0006] Water is a desirable vehicle for carrying ozone gas to and fromthe object or objects that are to be cleaned or sanitized. Variousmethods of diffusing ozone gas into water have been proposed in the art.However, prior art methods are generally inefficient and result in arelatively low concentration of diffused ozone. The method disclosed inthe above referenced patent to Siegel, for example, involves bubblingthe ozone gas into the water using a ceramic diffuser.

[0007] The effectiveness of ozone saturated water is limited by theconcentration of ozone gas which can be diffused into the water. Assuch, there exists a need in the art for a method and apparatus fordiffusing ozone gas into a liquid which produces a higher concentrationof ozone than has been possible heretofore.

SUMMARY OF THE INVENTION

[0008] The above described need which has existed heretofore in the artis fulfilled by an ozone diffuser according to the present inventionwhich includes an outer tube having a tubular porous membrane disposedcoaxially therein. An annular space is defined between the inner surfaceof the tubular member and the outer surface of the membrane into whichozone gas is applied.

[0009] Water is caused to flow through the interior of the membrane insuch a manner as to form a vortex which creates a negative pressure atthe inner surface of the membrane. The pressure difference between theannular space and the interior of the membrane causes ozone gas to besucked through the membrane and become diffused into the water.

[0010] The pressure difference results in a high concentration of ozonein the water. The vortex also produces a shearing effect which breaks upthe ozone bubbles and increases the diffusion efficiency.

[0011] These and other features and advantages of the present inventionwill be apparent to those skilled in the art from the following detaileddescription, taken together with the accompanying drawings, in whichlike reference numerals refer to like parts.

DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a simplified diagram illustrating a cleaning orsanitizing system including an ozone diffuser according to the presentinvention;

[0013]FIG. 2 is a side view of the present ozone diffuser;

[0014]FIG. 3 is a vertical sectional view of the diffuser taken on aline III-III of FIG. 2;

[0015]FIG. 4 is a horizontal sectional view illustrating a water inletof the diffuser taken on a line IV-IV of FIG. 2; and

[0016]FIG. 5 is a horizontal sectional view illustrating an ozone inletof the diffuser taken on a line V-V of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

[0017]FIG. 1 illustrates a cleaning or sanitizing system 10 including anozone diffuser 12 according to the present invention. In the illustratedconfiguration, the system 10 includes a tank 14 which contains objects(not shown), e.g. fruit or other agricultural products, which are to becleaned or sanitized.

[0018] Water having ozone gas diffused therein is circulated through thetank 14 in contact with the objects to be cleaned or sanitized. Morespecifically, a pump 16 draws water from the lower end of the tank 14through a conduit 18 and applies this water to a water inlet 20 of thediffuser 12 through a conduit 22 as indicated by arrows. Ozone gas froman ozone source 24 is applied to one or more ozone gas inlets 26 (onlyone inlet is shown) of the diffuser 12 through a conduit 28. Waterhaving ozone gas diffused therein is applied through a water outlet 30and a conduit 32 into the upper end of the water tank 14 through whichit circulates to clean or sanitize the objects therein.

[0019] The ozone source 24 per se is not the particular subject matterof the invention and will not be described in detail. The source 24 canbe constructed to convert oxygen gas into ozone gas using coronadischarge in a known manner.

[0020] The present ozone diffuser 12 is illustrated in FIGS. 2 to 5, andincludes an outer tubular member 40 which has an upper section 42 and alower section 44 which is fixed to the upper section 42 by a flange andbolt arrangement 46. The upper member 40 has a stepped inner surfaceincluding a large diameter surface 46 which terminates at its upper endin a small diameter surface 48. The lower member 44 has an inner surface50 with the same diameter as the surface 48.

[0021] A porous membrane 52 is coaxially mounted inside the member 40and has an outer diameter which is substantially the same as the innerdiameters of the surfaces 48 and 50. The membrane 52 is held at itsupper end within the surface 48, and at its lower end within the surface50. A first passageway 54 or annular space is defined between the innersurface 46 of the tubular member 40 and a first or outer surface 55 ofthe membrane 52. The upper end portion of the tubular member 40 and theinterior of the membrane 52 as defined by a second surface 57 thereofconstitutes a second passageway 56.

[0022] The diffuser 12 is oriented substantially vertically, with thelongitudinal axis of the second passageway 56 also being orientedvertically. The water inlet 20 opens into the upper end portion of thepassageway 56, whereas the water outlet 30 leads out of the lower endportion of the passageway 56. The ozone inlet 28 opens into, preferably,the central portion of the first passageway 54 and fills the passageway54 with ozone gas at a positive pressure. The passageway 54 does nothave an outlet.

[0023] In operation, water is applied through the inlet 20 into thesecond passageway 56. The tubular member 40 and membrane 52 areconfigured such that the water flows downwardly through the passageway56 in the form of a helical vortex as indicated by arrows 58. The vortexcreates a negative pressure on the inner surface of the membrane 52 dueto the Bernoulli effect as is known in the art per se. The pressuredifference between the opposite surfaces of the membrane 52 causes ozonegas to be sucked through the porous membrane 52 and become diffused intothe vortex of water flowing downwardly through the passageway 56.

[0024] The membrane 52 preferably has a porosity of 50 to 60 microns. Amembrane suitable for practicing the present invention is commerciallyavailable from Pore Technologies of Framinghan, Mass. The configurationwhich creates the vortex is preferably designed such that the pressuredifference between the opposite surfaces of the membrane 52 which causesthe ozone gas to be sucked therethrough is on the order of approximately5 to 20 psig, most preferably approximately 15 psig.

[0025] A preferred arrangement for creating the vortex is illustrated inFIG. 4. The longitudinal axis of the second passageway 56 is designatedas 60, and extends perpendicular to the plane of the drawing. The waterinlet 20 is oriented substantially perpendicular to the axis 60, and isradially offset therefrom. Thus, water flowing through the inlet 20impinges on the inner surface of the passageway 56 and is forced to spincounterclockwise as indicated by arrows in FIG. 4. The water is causedto flow downwardly through the passageway 56 by gravity. As such, thecombination of the circular flow caused by the offset of the inlet 20and the downward flow caused by gravity creates the desired helicalvortex.

[0026] The vortex also has a shearing effect on the ozone bubblesemerging from the inner surface of the membrane 52 which have a diameterof 50 to 60 microns. This shearing effect breaks up and scatters thebubbles into smaller bubbles having a diameter of 30 to 40 microns, andyet further increases the diffusion efficiency.

[0027] It has been determined that the present ozone diffuser 12 issubstantially more efficient than prior art diffusers, in that it iscapable of diffusing ozone into water with as much as 90% of thetheoretically maximum concentration of 6.75 milligrams per liter atambient pressure and temperature.

[0028] Various modifications will become possible for those skilled inthe art after receiving the teachings of the present disclosure withoutdeparting from the scope thereof.

[0029] For example, although the invention has been described as beingapplied to diffusing ozone gas into water, the scope of the invention isnot so limited and encompasses any application in which one fluid is tobe diffused into another fluid. One fluid can be a gas and the otherfluid can be a liquid as described above. Alternatively, both fluids canbe gasses or both fluids can be liquids. The porosity of the membraneand the pressure difference thereacross created by the vortex can bedetermined mathematically and/or empirically in accordance with aparticular application and the fluids which are to be mixed.

[0030] Various alternatives to the particular configuration which isexplicitly described and illustrated are also encompassed within thescope of the invention. For example, although a preferred embodiment ofthe invention is illustrated in which ozone is applied to the outer(annular) passageway 54 and water is applied to the inner passageway 56,it is within the scope of the invention to reverse this relationship.

[0031] Although not explicitly illustrated, in this particularembodiment ozone would be applied to the inner passageway and waterwould be applied to the outer (annular) passageway. A vortex created bywater flowing downwardly in the passageway would suck ozone from theinner passageway through the membrane into the water flow in the outerpassageway due to the pressure drop created by the vortex in a manneressentially similar to that described above. In this modification thelower end of the inner passageway would preferably be sealed such thatthe inner passageway would not have an outlet, and that an outlet beprovided at the lower end of the outer passageway.

[0032] It is further within the scope of the invention to provide othervortex creating water or other fluid flow paths and porous membranearrangements which cause ozone or another fluid to be sucked into thewater or other fluid through a membrane. Such paths can be, for example,circular, spiral, and/or include multiple sections which are similar ordifferent. Any configuration which produces the effect of diffusing onefluid into another fluid due to a pressure difference created on theopposite sides of a porous membrane by a vortex is considered to be anequivalent of the particular configuration which is described andillustrated.

What is claimed is:
 1. An apparatus for diffusing a first fluid into asecond fluid, comprising: a membrane having a porosity which issufficient to allow the first fluid to pass therethrough; a firstpassageway configured to apply the first fluid to a first surface of themembrane; and a second passageway configured to apply the second fluidto a second surface of the membrane which is opposite to the firstsurface thereof such that the second fluid forms a vortex withsufficiently low pressure to cause the first fluid to move from thefirst passageway through the membrane into the second passageway andbecome diffused into the second fluid.
 2. An apparatus as in claim 1 ,in which the first fluid is a gas and the second fluid is a liquid. 3.An apparatus as in claim 2 , in which the first fluid comprises ozonegas.
 4. An apparatus as in claim 3 , in which the second fluid compriseswater.
 5. An apparatus as in claim 1 , comprising an outer tubularmember, in which: the membrane is tubular and is disposed coaxiallyinside the outer tubular member; the first passageway comprises anannular space between an inner surface of the tubular member and anouter surface of the membrane, the outer surface of the membraneconstituting said first surface thereof; the first passageway has aninlet; the membrane has an inner surface which constitutes said secondsurface thereof and defines the second passageway; and the secondpassageway has an inlet and an outlet.
 6. An apparatus as in claim 5 ,in which: the inlet of the second passageway is oriented atsubstantially a right angle to a longitudinal axis of the secondpassageway and is radially offset from the longitudinal axis, therebycausing the second fluid to form said vortex in the second passageway.7. An apparatus as in claim 6 , in which the inlet and outlet of thesecond passageway are provided at substantially opposite ends thereof.8. An apparatus as in claim 7 , in which the apparatus is disposed suchthat the axis of the second passageway is oriented substantiallyvertically; and the inlet of the second passageway is disposed above theoutlet thereof.
 9. An apparatus as in claim 1 , in which: the firstfluid comprises ozone gas; and the membrane has a porosity ofapproximately 50 to 60 microns.
 10. An apparatus as in claim 1 , inwhich the first and second passageways are configured such that apressure difference between the first and second surfaces of themembrane is approximately 5 to 20 psig.
 11. An apparatus as in claim 1 ,in which the second passageway is configured such that said vortex atleast partially shears the first fluid at the second surface of themembrane.
 12. A method for diffusing a first fluid into a second fluid,comprising the steps of: (a) providing a membrane having a porositywhich is sufficient to allow the first fluid to pass therethrough; (b)applying the first fluid to a first surface of the membrane; and (c)applying the second fluid to a second surface of the membrane which isopposite to the first surface thereof in such a manner that the secondfluid forms a vortex with sufficiently low pressure to cause the firstfluid to move through the membrane and become diffused into the secondfluid.
 13. A method as in claim 12 , in which the first fluid is a gasand the second fluid is a liquid.
 14. A method as in claim 13 , in whichthe first fluid comprises ozone gas.
 15. A method as in claim 14 , inwhich the second fluid comprises water.
 16. A method as in claim 12 , inwhich: step (a) comprises providing the membrane in the shape of a tube;step (b) comprises applying the first fluid to an outer surface of themembrane which constitutes said first surface thereof; and step (c)comprises applying the second fluid to an interior of the membrane whichconstitutes said second surface thereof.
 17. A method as in claim 16 ,in which: the membrane is oriented such that a longitudinal axis thereofis oriented substantially vertically; and the second fluid is appliedinto the interior of the membrane at substantially a right angle to thelongitudinal axis and is radially offset from the longitudinal axis tocreate said vortex.
 18. A method as in claim 12 , in which: the firstfluid comprises ozone gas; and step (a) comprises providing the membranewith a porosity of approximately 50 to 60 microns.
 19. A method as inclaim 12 , in which steps (b) and (c) in combination comprise creating apressure difference between the first and second surfaces of themembrane of approximately 5 to 20 psig.
 20. A method as in claim 12 , inwhich steps (a), (b) and (c) in combination comprise creating saidvortex such that it at least partially shears the first fluid at thesecond surface of the membrane.